The present invention relates to a method of installing optical fibre cable elements, for instance combined groups of optical fibre ribbon cables, in ducts, and also to an arrangement for installing optical fibre ribbon cable elements, for instance combined groups of optical fibre ribbon cables, in ducts, for instance when installing such ribbon cables in duct systems that extend between a first collecting point for several subscriber optical fibre ribbon cables in an apartment building, tenement building or like multi-family building, and a second collecting point for further connection to one or more external fibre network systems.
It is known to install covered optical fibres in ducts by blowing air onto the fibres in order to lessen the strain on the fibres as they are installed. It is also known to blow optical fibre cables into ducts in order to install long, continuous lengths of optical fibre cables over long distances, such as to install optical fibre cables in so-called sub-ducts in kilometre lengths.
In order to enable fibre cable bodies fitted with electric contacts at one end to be installed in ducts, e.g. blown into said ducts, several optical fibre ribbons placed one upon the other to form an optical fibre ribbon cable body have been held together with the aid of an elastic tape which is wound helically around the optical fibre ribbons with a given overlap between successive turns. The helically overlapping elastic tape imparts to the cable body an external helical cross-sectional surface that can be acted upon by a passing air stream so as to cause the cable body to move in a desired direction in the duct in which it is to be installed. In addition to holding the fibre ribbon cables together, the tape wound around said body also enables the body to be driven forwards by the air. Alternatively, an optical fibre cable can be provided with a helically wound tape with a given overlap between successive turns, wherewith the resultant helically formed cross-sectional surface enables the cable to be propelled in a duct through the action of a by-passing air stream on said cross-sectional surface.
An optical fibre ribbon cable body that is fitted with electrical contact devices on one end can be installed conveniently over shorter distances, e.g. distances shorter than 300 metres. The invention avoids the necessity for extra splices and joins in conjunction with the installation of a blown fibre ribbon cable body or an optical fibre cable and also enables cost-effective and smooth installation of optical fibres to be achieved. The inventive method enables an optical fibre ribbon cable body to be fed into or blown into a hollow tubular section that has already been installed without danger of the positions of the ribbons being changed to any great extent in curved duct portions, and also enables a cable construction to be obtained in a relatively simple manner and at a cost which is lower than the cost incurred with a conventional cable that has a similar fibre content.
The invention will now be described in more detail with reference to a preferred embodiment thereof and also with reference to the accompanying drawings.